Yeah, 4th will still be on and very much so. You're looking at it as just the number of games left but you aren't considering the fixtures. While Tottenham is our biggest game remaining(Leicester and Sheffield United shouldn't be quite as tough as Spurs but tough nonetheless), Chelsea has still got to play Liverpool and City. So even with 6 points behind, I personally see Chelsea not getting anything in those game or at best 1 point, 3 if they get lucky.
Their fixture run in is just a lot more difficult than ours for it to be over after trailing 6 points behind while they still have City and Liverpool.
If we win against Tottenham(and I'm expecting us to do so) and starts strong, I see us sealing 4th before the final game. We continue with the form we left off and we;ll have breathing room while finishing off the season.